Late last week, Canada’s Atlantic coast was battered by Hurricane Fiona, with maximum sustained winds of around 90 mph (145 km/h). Hurricanes rarely maintain intensity this far north. Because? Hurricanes are fueled by high sea surface temperatures (SSTs) and ideally by high sea temperatures at great depth. As you move away from the tropics, SSTs tend to decrease.
But hurricanes aren’t limited to the warmer parts of the Atlantic, such as the Gulf of Mexico and the Caribbean Sea. Tropical systems often strengthen in these regions, but can sometimes persist or even strengthen elsewhere given favorable conditions. Ocean currents can transport warmer water poleward, which can produce regions at higher latitudes that have higher SSTs than their surroundings. Tropical systems that track north over warmer seas can maintain intensity or even strengthen, as happened with Hurricane Fiona.
Houses washed away in Newfoundland as Storm Fiona hits Canada – video
Fiona was first classified as a tropical depression on September 14, strengthening into a hurricane early on September 18. The hurricane made landfall in Puerto Rico later that day with maximum sustained winds of 85 mph (140 km/h), which also affected the Dominican Republic as it curved north. Fiona continued to strengthen over the next two days as the storm traveled over water that was warmer than average, reaching Category 4 early on September 21.
Over the next two days, Fiona remained a major hurricane as it moved to the north-northeast. Hurricanes typically curve eastward as they reach higher latitudes. But interactions with other weather systems can help to “pull” systems like Fiona north or even west. Fiona began interacting with an upper-level trough on September 23, and the hurricane accelerated toward Nova Scotia. Although SSTs are much lower near Nova Scotia than further south, they are currently more than 2C warmer than average, likely helping Fiona maintain hurricane-force winds.
Hurricane Fiona isn’t the only storm wreaking havoc, with Ian making landfall in the Caribbean and southeastern United States. Ian began life as a tropical storm in the Caribbean, strengthening to hurricane status on Monday, and is expected to become a major hurricane on Tuesday. Sustained wind speeds are likely to top 110 mph (177 km/h), with Ian tracking toward Florida and making landfall by Friday morning.